Apparatus for use in chemical digestions



June 1l, 1935.'

A, HENwooD 'ET AL .APPARATUS FOR USE IN CHEMICAL DIGESTIONS Filed Oct. 30, 1955 Patented June 11, 1935 APPARATUS Fon UsE IN CHEMICALv DIGEsTIoNs f Abraham Henwood, Cynwyd, and Raymond M.

Garey, Willow Grove, Pa.

Application October 30, 19 33,`Serial No. 695,916

y 10 Claims.

quantitative determinationk of nitrogen,- espevcially in organic materials. d

The principal object 4of `our invention is to provide an'economical apparatus byV which digestions of the Kjeldahl type may be carried out eilicientlyY Ywith the suppression of sulphuric acid mist and the accompanying elimination of the vspecial fume closet, the digestion room, and the expensive and complicated systems heretofore employed. t v i v `Another object of the present invention is to furnish *an apparatus for use in Kjeldahl digestions in which the escape o f the mist of sulphuric acid from the llask is prevented, while permitting the steam, sulphur dioxide, and carbon dioxide formed in the process of digestionrto escape freely, thereby vallowing the digestionto be carried out on the laboratory table without increasing pressure within the apparatus.`

1 Other objects will be apparent from a considi :eration vof the specification and claims. f

,In the accompanying drawing:

Figure l vis a perspective view of theapparatus of the present invention; and l Figure 2 is an enlarged fragmentary cross sectional viewy of the apparatus shown in Figure 1.

As is well known, Kjeldahl digestions, as conducted heretofore, have been` associated with the evolution from the digestion flask of very irritating and corrosive sulphuric acid mist which kcontinues throughout the digestion, requiring the use of special digestion closets or special digestion'rooms the atmosphereof which soon be.- comes .contaminated with the sulphuric acid fumes. K The attempts to abate this nuisance have usually been concerned with the disposal of the mist after its issuance from'v the digestion ilask, for example by placing the mouth of the flask through a hole ina lead pipe which in turn has an exit leading outdoors. In other instances, expensive and complicated apparatus has been suggested for use. The apparatus of the present invention approaches the problem from adifferent standpoint and effectively prevents the escape of the sulphuric acid mist from the digestion flask. The steam, sulphur dioxide, and carbon dioxide generated, however, are evolved from the ilask during the processin the same manner .as usually occurs so thatthe pressureinside the flask is not increased. Since the sulphuric acid mist fails to find its way into the room, the digestions when conducted inthe apparatus of the present invention may be performed on the open laboratory shelf without discomfort to the operator.

The apparatus of the present invention is characterized by a novel combination of the usual lKjeldahl flask and a porous acid-resistant septum n placed in the neck of the flask and'fltting closely therein, the septum being characterized by its ability to permit the free passage of gasesv therethrough but at the same time to preventthe esf ,i-

cape of sulphuric acid mist. `The septum also effectively prevents the setting up of convection currents of gases which in the ordinary procedure permits access of cold air tothe flask which chills the gas space of the flask and produces throughout this yspace agdense fogl or mistu of sulphuric acid. -With the apparatus of the` presentinvention no cold.` air gains admission and, therefore, the walls of the body of the flask act as a condensing surfacefor the sulphuric acid with yno accompanying condensation inthe gas space lof the ilask. The septum.. may ,be composed of a wide varietyy of materials sc longras it is inert to sulphuric acid vapors, andit is preferably ceramic in nature. For-example, it may be manufactured of alumina or silica grains sintered together, or a product resulting from the sintering of the grains of the oxides of the rare earthv elements Vmay be used. Preferably, the septum is in the form of an elongated hollow cylindrical member open at one end, the walls and other end of which are made of alundum (sintered alumina grains). The cylindrical member is so dimensioned with respect to the neck of the flask that it fits snugly therewithin so that the materials 4evolved during the digestion can only escape from the flask through the porous cylindrical member. The tube is also advantageously'ilanged at the top so that it may be supported on the vrflange ofthe Kjeldahl flask. If desired,` although it is not necessary, a stopper and delivery tube may be inserted in the mouth of the alundum tube, thus providing a means for'leading the-su1 phur dioxide, carbon dioxide, and steam intosoda lime or other convenient absorbent. 1

The preferred embodiment of the Iinvention is illustrated in the drawing where the usual Kjeldahl ilask is shown at I, with the alundum elongated hollow cylindrical member 2 fitting snugly Within the neck 'of the flask. The lower end of the cylindrical member 2 is also made of alundum and furnishes a closure for the cylindrical member as shown at 3. 'The tube has a flange 4 at the top thereof which fits over the'flange 5 at the neck of the flask, thus providing a support for the tube.

In'Kjeldahl digestions with the apparatus of the present invention, the procedure normally fol-1 lowed is employed. In a typical case, the flask is charged with the weighed material to be digested. Two or three granules of porous material are placed in the flask to insure smooth boiling and ten grams of potassium sulphate and twenty cubic centimetersV of concentrated sulphuric acid Es PATENT] oFFlc-Eff low the flange with a. small amount of filter paper in order to make doubly sure that the joint is tight. The flask containing the alundum hollow,

cylindrical member is placed in the usual position for digestion, for example at an angle in the s neighborhood of 45. Heat is suppliedto the bot tom of the flask by a small flame, for example three-quarters of an inch to one inch` high, and the heating is continued withl this flame for about fifteen minutes, during which time sulphur dioxide and carbon dioxideescape. The flame is then raised so that the tip touches the flask and the flask is heated until the material boils gently. Steam will be evolved froml the flask. When the steam has beenexpelled, the neck of the flask around the alundum hollow cylindrical member` cools as is indicated by the absence of accumula- "tion of water on a cold glass rod inserted inthe tube. The flame is raised further and boiling f continued until the'material in the flask is waterwhite, indicating that the g digestion is completed. The alundum hollow cylindrical member is removed from the flask when its contents have cooled. 'I'he hollow cylindrical member is filled with water which is allowed to flow into the flask Vducted in the usual manner. f Y The device of the present invention is simple,

yin order that any traces of spray containing ammonium sulphate will be returned to Vthe digested fluid 'in the flask, thereby permitting complete recovery. 'I'he material in the ask is then diluted to the usual volume, and distillation is concleanly, convenient, inexpensive, vand efficient, and permits the conductionof Kjeldahl digestions without the evolution of sulphuric acid mist from the flask. Considerable modification is possible in the construction of the septum and in the materials from which it is made without' departing from the essentialy features of our invention.

We claim:

1. An apparatus for use in Kjeldahl digestions, comprising a Kjeldahl flask and an acid-resistant septum fitting snugly Within the neck of said flask toprevent the formation of sulphuric acid fog by excluding cold air fromy said flask, such septum being pervious to the passage of gases but impervious tothe passage of sulphuric acid mist.

2. An apparatus for use in Kjeldahl digestions, comprising a Kjeldahl flask and an acid-resistant ceramic septum'tting'snugly within the neck of said flask to prevent the formation of sulphuric acid fog by Aexcludingcoldk air from said flask,

such septum being perviousy to the passage of gases but impervious to the passage `of sulphuric acid mist.

3. An apparatus for use in Kjeldahl digestions,` comprisingl a Kjeldahl flask and an acid-resistant alundum 'septum fitting snugly within the neck of said flask to prevent the formation of sulphuric acid fog by excluding cold air from said flask, such septum being pervious to vthe passage of gases but impervious tothe passage of Vsulphuric acid mist. n

4. An apparatus for use in Kjeldahl digestions, comprising a Kjeldahl flask and an acid-resistant septum in the form of an elongated hollow cylindrical member open at one end fitting snugly Within the neck of said flask to prevent the formation of sulphuric acid fog by excluding cold air from said ask, said septumfbeing. pervious to the passage of gases but impervious to the passage of sulphuric acid mist..

5. An apparatus for use in Kjeldahl digestions, comprising a Kjeldahl flask and an acid-resistant ceramic' septum in the form of an elongated hollow` cylindrical member open at one end fitting snugly within the neck of said flask to prevent the formation of sulphuric acid fog by excluding cold air from `said flask, said septum being pervious tothe passage of gases but impervious to the passage of sulphuric acid mist.

6. An apparatus for use in Kjeldahl digestions, comprising a Kjeldahl flask and an acid-resistant alundum septum in the form of an elongated hollow cylindrical member open at one end fitting snugly within the neckof said flask to prevent the formation of sulphuric acid fog by excluding cold air from said flask, saldseptumybeing pervious to the passage of gases but imperviousto the passage of sulphuric acid inist.

7. An apparatus for use in Kjeldahl digestions, comprisinga Kjeldahl flask andan acid-'resistant septum fitting snugly within the neck of said flask to prevent the formation of sulphuric acid fog by excluding-cold air from said flask,' said septum being in the form of an elongated hollow cylindrical member'open at one endv and having a'flange at said open end adapted to seat on the flange ofthe neck of said flask and being pervious tothe passage `of gases but impervious to ceramic septum kfitting snugly within the' neck of said flask to rprevent the formation of sulphuric acid fog by vexcluding Vcold air from said-"flask,`

said septum being in the form of an elongated hollow cylindrical member open at one endend having a flange at Vsaid open 'endadapted to'seat on the flange of the vneck of said flask and'being pervious to the passage of gases but impervious to the passage of sulphuric acid mist.

` 9. An apparatus for use in Kjeldahl digestions, comprising a Kjeldahl flask and an acid-resistant alundum septum fitting snuglywithin lthe neck of said flask to prevent the formation of sulphuric acid fog by excluding cold air from said flask, said septum being in vthe form'y of an elongatedhollo'w cylindrical member open at one 4end and having aflange latV said openend adapted-to seat on the flange' of vthe neck of said flask and being pervious toy the passage of gases but impervious to the passage Vof sulphuric acid mist'. v

l0. An apparatus for yuse in Kjeldahl digestions, comprising a Kjeldahl flask and an acidresistantporous Aseptum fitting' snugly Within the neck-y ofy said flask.` said septum being in the form of anelongated hollow cylindrical memberlopen 'at oneV end and having a flange yat said open end adapted to seat on the flange of the neck of said flask and being pervious to the passage of gases but impervious vto the passage of' lsulphuric acid mist and effectively preventing the setting kup oi convection currents of gases and the conse.- quent influx of coldai'rfwlththe formation of ymist-or fog inthe gas'spacefof the flask.

ABRAHAM HENwo'oD. RAYMOND M. Aeinem?. 

